Amp Gauge Wiring

[blancojp]

Hello All!
I am starting to wire up Stealth and noticed something that might present a problem to some, some other will not notice. Every Opel I have done never retained factory wiring, we used our own wiring methods and used our own fuse blocks. Stealth however is being wired as close to an original as possible, I even made a 9 circuit fuse block replacing the original.

The Amp gauge is wired in series with the complete electrical system supply of the car. In essence, it is not only displaying the charge rate but also total consumption of the vehicle. Even though this is functional and does not hurt anything (other than the gauge), it is still a mistake. The purpose of this gauge is to show how much current is being delivered to the battery by the charge system and nothing else. Instead of wiring the secondary wire from the gauge (red/white) to the center or supply stud on the fuse block, this wire should go directly to the stater stud where the battery is connected. Then a separate wire is taken from the same point back to the supply stud on the fuse block.

So to recap, the B+ terminal on the alternator goes to the gauge + terminal, the gauge - terminal back to the battery post on the starter. A 10 awg wire is then connected to the starter battery post and routed back to the fuse block post where the original red/white wire was. Very simple, accurate and easy way to make sure your gauge is not jumping all over (or pegged out) most of the time.

Maybe all of you have done this already and may have been corrected in other versions of the schematics, but I am using the original factory manual and it is all there.

Perhaps I should post a wiring section which shows how to use a 30A gauge with a 63A alternator.
Until next time...

[namba209]

JB, I really hate to disagree with you, but if the ammeter was designed to only show alternator output to the battery, there would be no need to have a negative side on the gauge. The ammeter was wired in, as you stated, to show consumption of the electrical system, except for the headlights, from the alternator, and also to show total consumption (negative side of the gauge) by the battery. On Willit? with the 105+ amp alternator, The gauge does indeed peg out for a few seconds after I start the engine, then drops down to under 10 amps, then slowly goes to the middle of the gauge, as the battery gets replenished after starting the engine. IMHO, having the gauge peg out, as it does after starting, doesn't do any harm to the gauge, as the internal buss bar can handle all the output of the alternator, and the shunt, which drives the needle, doesn't see all that amperage, it just indicates it.

[tekenaar]

Originally Posted by namba209 JB, I really hate to disagree with you, but if the ammeter was designed to only show alternator output to the battery, there would be no need to have a negative side on the gauge. The ammeter was wired in, as you stated, to show consumption of the electrical system, except for the headlights, from the alternator, and also to show total consumption (negative side of the gauge) by the battery. On Willit? with the 105+ amp alternator, The gauge does indeed peg out for a few seconds after I start the engine, then drops down to under 10 amps, then slowly goes to the middle of the gauge, as the battery gets replenished after starting the engine. IMHO, having the gauge peg out, as it does after starting, doesn't do any harm to the gauge, as the internal buss bar can handle all the output of the alternator, and the shunt, which drives the needle, doesn't see all that amperage, it just indicates it.

. . . you beat me to it!

[trlmr]

Namba is correct. if you change the wiring like you indicate and the load on the system is more than the alternator output it won't show the discharge. But a voltmeter would.

[blancojp]

Everyone has a different oppinion on the subject however this type of situation goes back to the sixties when amp gauges started making the scene. The gauge originally was placed in series with the supply line but was found to be a mistake, since the number of dead vehicles being towed in was scaling. On classic cars of the sixties and seventies, specialy GM vehicles, a central location for a return line from the amp gauge was determined to be one of the contacts on the horn relay; which was the centered supply line of the vehicle. Since then, all cars which have an Amp gauge installed follow somewhat the same norm and have cured many of the so called "Ghosts" which can appear. The shunt on the gauge is not strong enough to handle a constant large over current condition, will overheat and burn out as it has on many other models with VDO gauges.

A return line, as defined for the gauge and application, is a path which closes the circuit and allows current flow on a target device. In our case, the return line will only concentrate current flow on a specific circuit, which is the alternator. It is quite possible with the way the wiring is expressed on the drawings to show a charging status and actually be discharging the battery. And since the gauge is in series with the supply line, lose the gauge and the car is dead. My way you just lose the gauge, wonder why and keep going.

Again, right or wrong just thought it might be usefull information.

[trlmr]

I'll admit the original circuit is poor and you have a good point with the fact that if the amp gauge quits everything does. What you are doing will solve that problem. I'm sure that is the reason all of the newer vehicles have volt gauges. in retrospect I wish that when I had my gauges restored I had them replace the amp gauge with a volt gauge. I think they could have done that pretty easily and made it look original.

[wrench459]

Makes me wonder why the manufactures dumped the shunt ammeter and go with a voltmeter.

[namba209]

You're right of course JB, if you lose the ammeter, everything dies. I've been driving since the mid-fifties and never had that happen, of course back then, we only had generators. Personally, I'd like to have an ammeter in all my cars. They appear to be more accurate than the volt meters in cars today, and actually show rate of charge to the battery, whereas the volt meter just shows system voltage, indicated by a band of color and not actual numbers. Now if there was one that was accurate, with a range of 10-15 volts, I might be persuaded to install one, because it's so easy to do, and doesn't need the heavy gauge wires, along with an ammeter.

[markandson]

Along with these thoughts I also have a concern although I had not posted anything about it, I am pretty sure there have been some threads discussing it.

I put a 105 Amp alternator in my car, OK great, it works beautifully, except for the pegging ammeter as stated here, I also put a 100 amp fusible link at the alternator, again OK great, except for the fact that the 10 ga. wire that runs to the ammeter will be toast before the fusible link ever blows. I have already considered doing what JB suggests, I just have not spent the time to do it yet, seems to me that with all the extra stuff I have in my car it would be possible to have a melt down some day and lose the whole car .

[OriginalOpelGTOwner]

The Opel GT ampere meter only measures amperes from or to the battery. When the engine is running at or over 2000 rpm the ampere meter will measure zero amperes to the battery if the battery is charged even though the vehicle has an ampere electrical load while it is running which is connected to the alternator side of the meter. The real concern here is that most of the vehicle electrical load is switched through the ignition switch when you turn to key to run position. The ignition switch is the real weak link. With respect to ampere meters I would prefer a well calibrated voltage meter and an alternator indicator lamp. By the way, the headlamp load will read on the ampere meter when the engine is off or at idle with the stock 35 ampere alternator. The headlamp load is NOT through the ignition switch. Only the headlamp relay coil is. The 10 ga wiring in the Opel GT is only rated at 40 amperes. Next time you look at a new car with a 100 ampere alternator look at the wiring ga size. From the alternator it is 8 ga or heavier.

[markandson]

Originally Posted by OriginalOpelGTOwner The Opel GT ampere meter only measures amperes from or to the battery. When the engine is running at or over 2000 rpm the ampere meter will measure zero amperes to the battery if the battery is charged even though the vehicle has an ampere electrical load while it is running which is connected to the alternator side of the meter. The real concern here is that most of the vehicle electrical load is switched through the ignition switch when you turn to key to run position. The ignition switch is the real weak link. With respect to ampere meters I would prefer a well calibrated voltage meter and an alternator indicator lamp. By the way, the headlamp load will read on the ampere meter when the engine is off or at idle with the stock 35 ampere alternator. The headlamp load is NOT through the ignition switch. Only the headlamp relay coil is. The 10 ga wiring in the Opel GT is only rated at 40 amperes. Next time you look at a new car with a 100 ampere alternator look at the wiring ga size. From the alternator it is 8 ga or heavier.

I have to disagree, the wire from the alternator goes directly to the ammeter so whatever the alternator is putting out is going through the wire and the ammeter, the route from the alternator to the battery is through the ammeter so if you have a large draw on the system the alternator kicks in to make up what the battery can't supply. The statement about the 8 gauge wire is exactly my concern, I really need to add a wire to be able to carry the 100 amps that the alternator can produce!

[OriginalOpelGTOwner]

The Opel GT alternator meter only measures amperes to and from the battery, NOT total vehicle load when the engine is running. Above 2000 rpm the alternator is picking up 100% of the electrical load not the battery thus the meter reads zero. This is my assessment when I study the Opel GT electrical wiring diagram.

[markandson]

Originally Posted by OriginalOpelGTOwner The Opel GT alternator meter only measures amperes to and from the battery, NOT total vehicle load when the engine is running. Above 2000 rpm the alternator is picking up 100% of the electrical load not the battery thus the meter reads zero. This is my assessment when I study the Opel GT electrical wiring diagram.

The entire car is connected to the battery, so if you are supplying amps to the battery you are connected to the whole electrical system, it is a "make up" system, so the alternator will make up what the battery can't supply but eventually it equalizes when nothing is being turned on or off. There is no way the ammeter will "zero", anything the alternator puts out goes through it, if very little is turned on it may be almost zero since very little will be required to keep the car running, but it will be something.

[blancojp]

Originally Posted by OriginalOpelGTOwner The Opel GT alternator meter only measures amperes to and from the battery, NOT total vehicle load when the engine is running. Above 2000 rpm the alternator is picking up 100% of the electrical load not the battery thus the meter reads zero. This is my assessment when I study the Opel GT electrical wiring diagram.

The alternator runs and provides for the system when the sense (or sometime called field) circuit is enabled. This can happen at any time it is required. The gauge however is in series with the supply line to the fuse box. Whatever the current flow is, charge/discharge, the gauge will always measure. Even when the gauge shows a 0A or centerline, the alternator might be supplying up to 30A at that point just to keep up with demand.

And to answer a previous thread, a 10awg stranded wire can handle up to 68A at 12Vdc in a short run. In any event, a 105A alternator will require at least a #6 from the supply to the gauge and another #6 from the gauge to the fuse block. Bear in mind also the Opel fuse box rating for the buss connectors is 45A so changing the wire alone is not going to fully cure the problem.

[namba209]

After going through my DESTEC schematic, which is as accurate as the FSM, but easier to read, I noted the following: The ammeter is wired in parallel with the alternator output, so it only shows what's going in to the battery, not total consumption of alternator output. By the same token, when the engine is at idle and the ammeter is on the negative side, it does show total draw from the battery. So, yes indeed, the ammeter shows what gozinto and outa the battery, but not total load when the engine is running. BUT, as noted earlier, except for a few items, headlights, radio, courtesy light, rear window defog, clock, and key buzzer, everything goes through the ignition switch. Which is a good reason to not only install an "OttoStart" relay, but also an additional 40 amp relay off the run side of the ignition switch, to save both the run and start contacts inside the switch. Going back to concerns on using the higher 100+ amp alternator, it shouldn't be a problem. The high amp rating is what the maximum output is, not the system draw. The Opel electrical engineers figured that a 35 amp alternator could keep up with the system, so a higher amp alternator would just be icing on the cake at lower RPMs. To put this in perspective, I'm running a 20 amp circuit breaker for the headlights and haven't had a problem, so far.

[markandson]

Originally Posted by namba209 I noted the following: The ammeter is wired in parallel with the alternator output

Ron, Not to beat a defunct horse but an ammeter will not read anything if wired in parallel, it has to be in series, a volt meter would be wired in parallel. As far as my GT's electrical system I did add a second fuse block with 6 circuits on it and ran its power direct from the lug on the starter. The main power from that starter lug runs through a 40amp relay which is powered up by the ignition switch to avoid any additional load on the switch. The added equipment still puts a load on the whole system which is getting its power from the 105 amp alternator which is feeding through the 10ga wire and the ammeter, so with enough stuff on the power requirement might approach the capacity of the wire.
JMTCW

[wrench459]

Originally Posted by markandson Along with these thoughts I also have a concern although I had not posted anything about it, I am pretty sure there have been some threads discussing it. I put a 105 Amp alternator in my car, OK great, it works beautifully, except for the pegging ammeter as stated here

Originally Posted by wrench459 you'll need a longer shunt wire to correct the amp gauge in the 3 X factor that might be 1 inch,2 inch or even a three inch

, I also put a 100 amp fusible link at the alternator, again OK great, except for the fact that the 10 ga. wire that runs to the ammeter will be toast before the fusible link ever blows. I have already considered doing what JB suggests, I just have not spent the time to do it yet, seems to me that with all the extra stuff I have in my car it would be possible to have a melt down some day and lose the whole car .[/QUOTE]

[trlmr]

http://www.rbeelectronics.com/wtable.htm
the major confusion here seems to be the load capacity of 10 gauge wire. I don't know how long the cable is from the alt to the fuse box is but 10 ft seems reasonable. The link I posted says it should be enough unless your battery is completely dead or you are running a 300 watt stereo or something like that. You will notice that opel didn't bundle the alt cable to closely to other wires so that should help with heat dissipation also.

[namba209]

Jeff, you're correct, I misread the schematic. I can claim a senior moment here, I had the painter here at the time, doing the exterior of the house. The actual path is from the alternator, through the ammeter, then the ignition switch, to the fuse panel. I don't know if you followed the thread on Willit?, but I added an additional 13 circuits and 7 relays, all going to a power panel I made using 20 aircraft style circuit breakers. I used the original Opel harness and integrated it with the harness that came with the V-6, using quick disconnect plugs just below and outboard of the clutch/brake pedals in the engine compartment. One thing I noted, is the V-6 and Opel alternator wires were the same size, as are the starter solenoid wires. So referring back to your original post as to whether the alternator wire is sufficient to handle the output of the alternator, I would suggest it is, if you consider a 95 Camaro would have similar or more accessories than the Opel would. But then you have to remember I'm just a wrench turner, not an electrician. HTH.

[markandson]

Originally Posted by trlmr Wire Gauge Tables the major confusion here seems to be the load capacity of 10 gauge wire. I don't know how long the cable is from the alt to the fuse box is but 10 ft seems reasonable. The link I posted says it should be enough unless your battery is completely dead or you are running a 300 watt stereo or something like that. You will notice that opel didn't bundle the alt cable to closely to other wires so that should help with heat dissipation also.

Interesting, according to the table, assuming the length of wire in the car is about 5' from the alternator to the ammeter we should be good for 150 amps, more than enough, so it's just the ammeter that would be a concern. I did notice the same thing as posted above, that when I first start the car it pegs at 30 amps and then quickly goes down to a lesser value.

[guyopel]

I have been using the 105 amp.alt. with no problems .
This site is very helpful with ele. questions :
MadElectrical.com - Electrical Tech
HTH
John

[blancojp]

Originally Posted by guyopel I have been using the 105 amp.alt. with no problems . This site is very helpful with ele. questions : MadElectrical.com - Electrical Tech HTH John

If you have an Opel with all factory components and acessories, your total consumtion is less than 30A. If you have a car like mine with all sorts of power components and a/c, your consumption will be higher therefore the electrical system needs to be beefed up.

The length of the wire from the alternator to the supply point is over 10' since the gauge is in series and considered a link between the two wires. But if you want to know how much your car needs, turn the ignition switch on without starting the engine and turn on everything on the car. Then use a clamp on ampmeter and see what it reads. Once a figure is obtained, add 30% to it and you have a very close estimate on what your car needs.

Since I have worked in power generation, hydraulics and controls most of my life, I have seen and experienced Mr. Murphy at work. So every electrical circuit I build has a 20-30% added capacity for that wonderfull day that Mr. Murphy decides to pay you a visit. So don't be affraid to go larger on the supply, you might find yourself at an advantage some day.

[markandson]

Originally Posted by blancojp The length of the wire from the alternator to the supply point is over 10' since the gauge is in series and considered a link between the two wires.

Excellent point, I totally agree. So using the table we would be right at 100 amps.

[blancojp]

Originally Posted by markandson Excellent point, I totally agree. So using the table we would be right at 100 amps.

Not to knock your efforts but I would not put too much stock on that table, some of the values quite don't make it. If you look at the 15' range, at 100A it drops to a #6awg from a #10awg.

The correct way is to use a NEC table to determine what you need. As an example, NEC says that 10 feet of 10awg wire at 90 degrees celsious will carry a maximum of 42.5A with a voltage drop of 3%. This means that at charging voltage (minus the loss) the system can safely see a maximum of 45A.

Always use the tools of the trade when calculating since some of the available tables tend to be conditionally flaky.

[markandson]

Originally Posted by blancojp Not to knock your efforts but I would not put too much stock on that table, some of the values quite don't make it. If you look at the 15' range, at 100A it drops to a #6awg from a #10awg. The correct way is to use a NEC table to determine what you need. As an example, NEC says that 10 feet of 10awg wire at 90 degrees celsious will carry a maximum of 42.5A with a voltage drop of 3%. This means that at charging voltage (minus the loss) the system can safely see a maximum of 45A. Always use the tools of the trade when calculating since some of the available tables tend to be conditionally flaky.

Well if that is the case then we are right back where I started which is to say that the 10ga wire is not enough for the 105amp alternator.